Magnetic lifting element

ABSTRACT

A magnetic lifting element for shipping cages such as poultry coops in the form of a flat pad comprising magnetic material and having hook members extending from the bottom of the pad for engaging the edges of holes in the top of the cage. The shanks of the hook member are longer than the thickness of the cage top to permit at least approximately one-half inch vertical displacement of the pad from the top of the cage after the hook members are inserted through the holes for accommodating possible vertical misalignment between an elongated magnetic pickup boom and the tops of a row of cages to be loaded on or off a truck.

United States Patent 1191 Box July 15, 1975 4] MAGNETIC LIFTING ELEMENT[76] Inventor: Theodor M. Box, 1108 Aileen Rd., Hammer-Ham BroomBrielle, NJ. 08730 22 Filed; Oct. 7, 1974 [571 ABSTRACT Appl. N0.:512,880

A magnetic lifting element for shipping cages such as poultry coops inthe form of a flat pad comprising magnetic material and having hookmembers extend- [52] US. Cl. 335/286; 206/818; 335/295 i f h b tt m ofthe pad for engaging the edges [5 l] Int. (1 B23) 3/l54 of hgles in thetop of the cage, The shanks of the hook 1 Field of Search 335/236, 1284, 294, member are longer than the thickness of the cage top 335/295,270; 220/ 06; 206/8 3 to permit at least approximately one-half inchvertical displacement of the pad from the top of the cage afterReferences cued the hook members are inserted through the holes forUNITED STATES PATENTS accommodating possible vertical misalignment be-3,250,962 10/1966 Palme 335/295 twee" elongated magnetic Pickup boom and3335.378 8H9 Corvino u 335/236 tops of a row of cages to be loaded on oroffa truck. 3,363,209 [/1968 levar 335/295 3.528.583 9/1970 Taylor220/306 3 4 Drawmg F'gures .7 7.0 \7 i l I 8 MAGNETIC LIFTING ELEMENTBACKGROUND OF THE INVENTION This invention relates to magnetic liftingdevices and particularly to pads of magnetic material for liftingshipping cages by means of electromagnetic booms.

When shipping poultry it is customary to place about a half dozen birdsin each of a number of openwork cages or coops and then to fill a longtruck bed with rows of coops stacked several layers deep. with well overone hundred coops per truck. To unload the cages individually by manuallabor is time-consuming and subjects the birds to possible injury byrough handling of the cages.

The unloading process has been mechanized by some shippers who fastensteel plates to the top of each cage, one plate near each end. byscrewing. bolting or welding the plate directly to the cage. A boomfitted with electromagnets can then be lowered into contact with theplates on the cage, the magnets energized. and the cage lifted off thetruck to any desired location.

The unloading process can be speeded still further by using an extendedboom capable of picking up several cages in a horizontal rowsimultaneously. It is necessary that the cage tops be almost perfectlyaligned in a plane, however. because the attractive force of the magnetsfalls rapidly as the gap between the boom and the lifting plateincreases. Since such perfect alignment is rarely achieved in practice,usually one cage, or only a few at most. can be unloaded at a time.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a magnetic lifting element for shipping cages that will permitunloading and loading a horizontal row of cages extending the entirewidth or length of a truck bed.

It is another object of the invention to provide a magnetic liftingelement for shipping cages that can be easily installed in the field.

Another object of the invention is to provide a mag netic liftingelement of simple. one-piece design.

A more specific object of the invention is to provide a one-piecemagnetic lifting for a shipping cage that can be permanently attached tothe cage with fastening means that permit substantial vertical movementof the lifting element with respect to the cage top.

These and other objects are accomplished by a magnetic lifting elementthat comprises a flat pad, at least the major portion of which consistsof magnetic material. at least one attachment member extendingapproximately perpendicularly from one face of the flat pad, and atransverse stop means located near the outer end of the attachmentmember. The attachment member is adapted to be inserted loosely throughan opening in the top ofa shipping cage. such as an openwork poultrycoop. and the stop means is adapted to engage the under surface of thecage top adjacent to the edge of the hole to prevent withdrawal of theattachment member after it has been inserted through the hole.

An important feature of the invention is that the stop means is spacedfrom the one face of the pad by a distance substantially greater thanthe thickness of the cage top to allow vertical movement of the flat padaway from the upper surface of the cage before the stop member engagesthe under surface for accommodating possible vertical misalignmentbetween a pickup boom and the top of the cage. The spacing of the stopmeans should allow for at least about one-half inch of vertical movementand can be even more. depending on the field strength of the boomclectromagnet. Since the relatively light magnetic lifting element isfree to move by itself under the influence of the electromagnetic fieldupward into contact with the boom, a given magnet strength is effectiveacross a much greater gap than when the entire weight of a filled cagemust be lifted.

A preferred embodiment of the invention includes at least two attachmentmembers, each member having a side that is substantially perpendicularto the one face of the flat pad, the side of one attachment memberfacing in an opposite direction from the side of the other attachmentmember, and the two sides being spaced apart to provide loose slidingcontact by said sides with corresponding edges of at least one holethrough the top of a shipping cage when the attachment members areinserted therethrough.

The transverse stop means preferably comprises a wedge-shaped hookportion integrally formed at the outer end of each attachment member,each hook portion having a sloping face for engaging at an angle thecorresponding edge of the hole to facilitate insertion of the attachmentmember and a rear portion extending from the side of the attachmentmember for engaging the undersurface of the cage top adjacent to theedge of the hole after the attachment member has been inserted.

In one preferred form, the magnetic lifting element consists of a singleiron casting. This form is particularly adapted for mounting on a moldedplastic poultry shipping cage of the type that has a flat top surfaceapproximately one-quarter inch thick pierced by rows and columns ofrectangular openings to form a lattice like grid. The plastic issufficiently resilient to permit insertion of the integral attachmentmembers. which are too stiff themselves to bend appreciably. At the sametime the plastic is strong enough to resist pulling out of the stopportions of the attachment members after insertion.

Such a type of plastic poultry cage is disclosed in my U.S. Pat. No.3,754,676, issued on Aug. 28. i973. The cage of that patent alsoincludes integral longitudinal and transverse vertical stiffening websthat divide the upper surface of the cage into rectangular wells havingat least one of the rectangular openings at the bottom of each well. Theflat pad of the cast iron lifting element is preferably a rectangularplate having a thickness approximately equal to the height of the websand being sized to fit loosely within one of such wells with the topapproximately flush with the tops of the stiffening webs.

Another preferred embodiment is in the form of a rectangular magneticmetal plate tightly encased in a plate holder of molded plasticenclosing the edges and bottom of the metal plate. The attachmentmembers are integrally formed as extensions of the plate holder. Beingmade of plastic these attachment members may have some slight resiliencyso as to bend when the hook portion is inserted into an opening in thecage top. This feature makes the plastic-enclosed steel plate type ofmagnetic lifting element particularly suitable for use with metalpoultry cages, either of welded wire or stamped sheet metal, or evenwith wood cages that are too stiff to deflect when the attachmentmembers are being inserted.

In an especially preferred design of the plasticencased embodiment. theedges of the metal plate are bevelled outwardly from the top of theplate to the bottom to securely wedge the plate into the plate holder.although other keying elements such as ridges or ribs may be used. ifdesired.

The foregoing and other features of the magnetic lifting element of thepresent invention will be more fully described in connection with thepreferred embodiments as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of apoultry shipping cage having two magnetic lifting elements mounted onthe top.

FIG. 2 is a perspective view of a lifting pad embodiment prior toinsertion through openings in the top of a shipping cage.

FIG. 3 is a side view in partial section of a plasticencased alternateembodiment of a magnetic lifting pad after insertion through openings inthe top of a shipping cage.

FIG. 4 is a side view of an electromagnetic pickup boom engagingmagnetic lifting elements of separate cages in a horizontal row.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In reference to FIG. 1. a pairof magnetic lifting elements are shown mounted on the top of a moldedplastic poultry shipping cage ll. The cage is of the type disclosed inthe above-mentioned U.S. Pat. No. 3.754.676 in which the top. bottom.and sides are formed as basically flat sheets pierced by columns androws of rectangular ventilation holes and strengthened by integrallongitudinal and transverse external webs. Specifically. the top of cageII is in the form of a flat sheet 12 pierced by rectangular openings 13to produce a lattice-like grid pattern. Longitudinal stiffening webs l4and transverse stiffening webs 15. formed integrally with flat sheet 12.divide the upper surface of the cage into rectangular wells eachenclosing at least one of the rectangular openings.

Each magnetic lifting elements I0 is in the form of a flat rectangularpad I6 sized to fit loosely within one of the rectangular wells on theupper surface of the cage top. the thickness of the pad beingapproximately the same as the height of the stiffening webs so that thetop of the pad is about even with the top edges of the webs.

As shown more clearly in FIG. 2, at least one attach ment member. suchas hook members 17. extends approximately perpendicularly from the lowersurface of flat pad 16 for loose-fitting insertion through openings I3in the bottom of the well. Each hook member in cludes a shank portion 18having a face 19. a transverse stop portion 20 extending from the facenear the lower end of the shank portion. and a sloping end portion 2lextending from the outer edge ofthe stop portion to the tip of the hookmember. Depending on the number and arrangement of openings in the cagetop that are spanned by the flat pad. more than one attachment membermay be used to hold the pad to the top of the cage. In the illustratedembodiments. for example. a pair of oppositely facing hook members arepositioned adjacent to opposite edges of the pad. The sloping endportion of each hook member engages an adjacent edge of one of theopenings 13 to facilitate insertion of the hook members through theopenings. After insertion. the stop portion of each hook member engagesthe under surface of flat sheet 12 when the lifting element is raised,to prevent removal of the element from the cage.

As mentioned earlier. it is an important feature of the presentinvention that the stop portion of each hook member is spaced from thebottom face of the pad by a distance substantially greater than thethickness of the top surface of the cage. preferably at least twice thatthickness. to allow vertical movement of the flat pad away from theupper surface of sheet 12 before the stop portion engages the undersurface of the sheet for accommodating possible vertical misalignmentbetween an electromagnetic pickup boom and the top of the cage.

For example. the thickness of sheet 12 may be about one-quarter inch fora molded plastic cage of the type illustrated in the drawing. and thespacing of the stop portion of each book member from the bottom of thepad may range from about one-half inch to one inch or more. beingpreferably about three-quarters of an inch for the applicationillustrated. The spacing chosen for any particular size of liftingelement will depend primarily on the maximum vertical distance acrosswhich the electromagnetic boom can attract the element.

The lifting element embodiment of FIG. 2 consists of a single piece ofmagnetic material such as steel or iron. A particularly inexpensivemethod of manufacture is to make the element as an iron casting. Thehook elements of such a casting will be essentially inflexible. butthere is sufficient resilience in the plastic material of the cage topto permit insertion of the hook members past the adjacent edges of theopenings without causing permanent deformation.

FIG. 3 shows an alternative embodiment of the magnetic lifting elementof the invention that may be used with shipping cages of relativelyresilient plastic. such as high impact plastic. but that is even moresuitable for cages of metal. wood. or other material that cannot beresiliently deformed to the extent necessary to allow insertion of thehook member. In this alternative embodiment the lifting elementcomprises a rectangular steel plate 22 that is tightly encased in amolded plastic plate holder 23 in the form of a flat. open-top boxsurrounding the edges and bottom of the plate. The plate holder hasintegrally molded hook members 17' similar to the hook members of theall metal embodiment of FIG. 2.

To insure a tight fit of the plate in the plate holder the edges of theplate are bevelled outwardly from top to bottom to wedge the plate intothe plate holder. Although this is a particularly simple arrangement.inexpensive to fabricate. other forms for accomplishing the same purposecan be used. such as ribs. grooves. or steps arranged to lock the plateinto the plate holder.

The plate holder is preferably molded from thermoplastic material havingsome inherent resiliency so that the shanks 18' of the hook members willact as leaf springs to yieldably permit the sloping end portions 21' tobe inserted past the adjacent edges of openings 13, the shanks thenstraightening so that surfaces 20 will engage the under side of the cagetop when the lifting elements are raised by a magnetic boom.

FIG. 4 illustrates the operation of the magnetic lifting elements of thepresent invention and particularly shows the advantage resulting fromallowing relative vertical movement of each element away from the cagetop before the stop means engages the under surface of the top. In FIG.4 an elongated horizontal electromagnetic boom 24 is positioned over arow of shipping cages ll equipped with magnetic lifting elements 10, twoof which are shown.

When a row of cages are placed on a truck. the tops of the cages areoften not completely aligned in one plane due to irregularities of thetruck bed surfaces or small differences in the height of the cages.Consequently. the boom may contact only one or two of the magneticplates, and there will be an air gap of as much as one-half inch or morebetween the bottom of the boom and the top surfaces of the lowest platesin the row.

If the plates are rigidly fastened to the cages, the boom magnets mustbe powerful enough to attract the plates against gravitational forceacting on the entire filled cage. By spacing stop surfaces from thebottom of flat pads 16 by a distance substantially greater than thethickness of sheet 12, the pads move freely upward into contact with thelower surface of boom 24 when current is turned on to the electromagnetsbefore surfaces 20 engage the under side of sheet 12. Thus, verticalmisalignment between cages. as shown in the drawing. is accommodatedwithout requiring excessively powerful boom magnets. The limited freevertical travel of the lifting elements also prevents a sudden shock tothe poultry or other contents of the shipping cages when theelectromagnet current is first turned on and the lifting elements snapinto contact with the boom. After the plates have made contact, the magnetic attraction force is fully strong enough to lift the full cageswith the boom for placement at any desired location.

As a specific example for use with poultry shipping coops of the typedescribed, two magnetic lifting elements have been used with one cage.each element having a flat steel pad approximately 3 inches by 5 inchesby inch in size and having a hook member shank length sufficient toprovide approximately /2 4 inch of free vertical movement of the padwith respect to the cage top. Other sizes and weights of shipping cagesmay require different dimensions of lifting elements, as may bedetermined easily by experiment.

I claim:

1. A magnetic lifting element for mounting on top of a shipping cage topermit lifting the cage by means of an electromagnetic pickup boom, thecage having at least one opening through the top thereof, wherein thelifting element comprises:

a flat pad, the major portion of which is composed of magnetic material;

at least one attachment member extending approximately perpendicularlyfrom one face of the flat pad for loosefitting insertion through theopening in the top of the cage; and

a transverse stop means located near the outer end of the attachmentmember for engaging the under surface of the cage top to preventwithdrawal of the attachment member after it has been inserted throughsaid opening. the transverse stop means being spaced from the one faceof the pad by a distance substantially greater than the thickness of thecage top to allow VEIZIiCfil movement of the flat pad away from theupper surface of the cage before the stop member engages the undersurface for accommodating possible vertical misalignment between thepickup boom and the top of the cage.

2. The magnetic lifting element of claim 1 including at least twoattachment members. each attachment member having a side that issubstantially perpendicular to the one face of the flat pad, the side ofone attachment member facing in an opposite direction from the side ofthe other attachment member, and the two sides being spaced apart toprovide loose sliding contact by said sides with corresponding edges ofthe at least one opening through the top of the cage when the attachmentmembers are inserted therethrough. and the transverse stop meanscomprises hook portions integrally formed at the outer end of eachattachment member, each hook portion having a sloping face for engagingat an angle the corresponding edge of the at least one opening in thetop of the cage to facilitate insertion of the attachment memberstherethrough and a rear portion extending from the perpendicular side toengage the under surface of the cage top adjacent to the correspondingedge of the opening after the pad is mounted on the top of the cage.

3. The magnetic lifting element of claim 1 wherein the transverse stopmeans is spaced from the one face of the pad by a distance sufficient toallow vertical movement of at least one-halfinch of the flat pad awayfrom the upper surface of the cage.

4. The magnetic lifting element of claim 1 wherein the element is madeof cast iron.

5. The magnetic lifting element of claim I wherein the flat padcomprises:

a rectangular magnetic metal plate and a plate holder in the form of aflat. open-top box of molded plastic material tightly encasing the edgesand bottom of the metal plate.

6. The magnetic lifting element of claim 5 wherein the edges of themagnetic metal plate are bevelled outwardly from the top of the plate tothe bottom of the plate to wedge the plate into the plastic plateholder.

7. A magnetic lifting element particularly adapted for mounting on amolded plastic poultry shipping cage of the type having a top surfacepierced by rows and columns of openings to form a lattice-like grid andreinforced by integral longitudinal and transverse vertical webs thatdivide the upper surface of the cage top into rectangular wells eachenclosing at least one of the openings, the lifting element comprising:

a flat rectangular pad comprising magnetic material and sized to fitloosely within one of the rectangular wells on the upper surface of thecage and a plurality of hook members extending from the bottom face ofthe pad adjacent to opposite edges thereof. each hook member including ashank portion having a face substantially perpendicular to the bottomface of the pad for making loose sliding contact with an adjacent edgeof the at least one opening enclosed by the well a transverse stopportion extending from the face of the shank near the lower end of thehook member for engaging the under surface of the cage top after thehook member has been inserted through the hole, the stop member beingspaced from the bottom face of the pad by at least twice the thicknessof the top surface of the cage to allow vertical movement of the pad outof the well before the stop member engages the under surface of the cagetop, and a sloping end portion extending from the outer edge of the stopportion toward the tip of the hook member for engaging at an angle theadjacent edge of the opening to facilitate insertion of the hook member[here through.

8. The lifting element of claim 7 consisting of a single piece ofmagnetic metal.

1. A magnetic lifting element for mounting on top of a shipping cage topermit lifting the cage by means of an electromagnetic pickup boom, thecage having at least one opening through the top thereof, wherein thelifting element comprises: a flat pad, the major portion of which iscomposed of magnetic material; at least one attachment member extendingapproximately perpendicularly from one face of the flat pad forloosefitting insertion through the opening in the top of the cage; and atransverse stop means located near the outer end of the attachmentmember for engaging the under surface of the cage top to preventwithdrawal of the attachment member after it has been inserted throughsaid opening, the transverse stop means being spaced from the one faceof the pad by a distance substantially greater than the thickness of thecage top to allow vertical movement of the flat pad away from the uppersurface of the cage before the stop member engages the under surface foraccommodating possible vertical misalignment between the pickup boom andthe top of the cage.
 2. The magnetic lifting element of claim 1including at least two attachment members, each attachment member havinga side that is substantially perpendicular to the one face of the flatpad, the side of one attachment member facing in an opposite directionfrom the side of the other attachment member, and the two sides beingspaced apart to provide loose sliding contact by said sides withcorresponding edges of the at least one opening through the top of thecage when the attachment members are inserted therethrough, and thetransverse stop means comprises hook portions integrally formed at theouter end of each attachment member, each hook portion having a slopingface for engaging at an angle the corresponding edge of the at least oneopening in the top of the cage to facilitate insertion of the attachmentmembers therethrough and a rear portion extending from the perpendicularside to engage the under surface of the cage top adjacent to thecorresponding edge of the opening after the pad is mounted on the top ofthe cage.
 3. The magnetic lifting element of claim 1 wherein thetransverse stop means is spaced from the one face of the pad by adistance sufficient to allow vertical movement of at least one-half inchof the flat pad away from the upper surface of the cage.
 4. The magneticlifting element of claim 1 wherein the element is made of cast iron. 5.The magnetic lifting element of claim 1 wherein the flat pad comprises:a rectangular magnetic metal plate and a plate holder in the form of aflat, open-top box of molded plastic material tightly encasing the edgesand bottom of the metal plate.
 6. The magnetic lifting element of claim5 wherein the edges of the magnetic metal plate are bevelled outwardlyfrom the top of the plate to the bottom of the plate to wedge the plateinto the plastic plate holder.
 7. A magnetic lifting elementparticularly adapted for mounting on a molded plastic poultry shippingcage of the type having a top surface pierced by rows and columns ofopenings to form a lattice-like grid and reinforced bY integrallongitudinal and transverse vertical webs that divide the upper surfaceof the cage top into rectangular wells each enclosing at least one ofthe openings, the lifting element comprising: a flat rectangular padcomprising magnetic material and sized to fit loosely within one of therectangular wells on the upper surface of the cage and a plurality ofhook members extending from the bottom face of the pad adjacent toopposite edges thereof, each hook member including a shank portionhaving a face substantially perpendicular to the bottom face of the padfor making loose sliding contact with an adjacent edge of the at leastone opening enclosed by the well, a transverse stop portion extendingfrom the face of the shank near the lower end of the hook member forengaging the under surface of the cage top after the hook member hasbeen inserted through the hole, the stop member being spaced from thebottom face of the pad by at least twice the thickness of the topsurface of the cage to allow vertical movement of the pad out of thewell before the stop member engages the under surface of the cage top,and a sloping end portion extending from the outer edge of the stopportion toward the tip of the hook member for engaging at an angle theadjacent edge of the opening to facilitate insertion of the hook membertherethrough.
 8. The lifting element of claim 7 consisting of a singlepiece of magnetic metal.